externalDTD
Returns a DTD validator based on the external subset of the document.

internalDTD
Returns a DTD validator based on the internal subset of the document.

public_id
Returns the public ID of the DOCTYPE.

root_name
Returns the name of the root node as defined by the DOCTYPE.

standalone
Returns the standalone flag as declared by the document. The possible
values are True (standalone='yes'), False
(standalone='no' or flag not provided in the declaration),
and None (unknown or no declaration found). Note that a
normal truth test on this value will always tell if the
standalone flag was set to 'yes' or not.